Triangles to Quads Problem
Circles and Quads are always a strange mix.

You can use Grid Fill to get quads.

Go to CtrlF or Mesh->Faces->Grid Fill on the menu. 
Or just press the space bar and type Grid Fill.

Pressing F6 will bring out the different options for the tool (or you can set them on the Grid Fill tab that appears on the Left Side of the screen by pressing T)



Other option to deal with edges on a cylinder is  to select the edge, extrude (E) and scale to bring the edges in, then extrude again and press Esc without moving the mouse. Then just merge the edges at the center AltM into a pole. This oPtion will give you some triangles, but in a manageable topology.



Other way to deal with the issue is selecting the edge and using Fill F. That will create a N-gon. 

Then you can use inset (I). To fill the center you can choose then between an N-gon (Using fill again) or triangles with a common pole.